1. Field of the Invention
The present invention relates to a multi-eye image sensing apparatus having a plurality of image sensing systems.
2. Description of Related Art
Conventionally, as a method of sensing a three-dimensional image of an object, a method using a multi-eye image sensing apparatus having a plurality of image sensing optical systems is known. In this image sensing method, an object is sensed using a plurality of image sensing systems, e.g., two, right and left image sensing systems, and the three-dimensional shape of the object is recognized by disparity produced between the right and left image portions of the object sensed by the right and left image sensing systems. Such three-dimensional shape recognition works in basically the same way a person recognizes the shape of an object as a three-dimensional shape due to disparity produced upon capturing the object by the right and left eyes.
In image sensing using the multi-eye image sensing apparatus, the base length (spacing between the right and left image sensing systems) and convergence angle (the angle the optical axes of the right and left image sensing systems make with each other) are changed depending on the distance to an object (i.e., a far object or near object). This is done to capture the overlapping region between the right and left images since the region changes depending on the distance to the object (i.e., a far object or near object). For example, when the right and left image sensing systems are placed parallel to each other, the overlapping region becomes narrower as the object becomes closer. In order to assure this overlapping region upon image sensing, the optical axis directions of the right and left image sensing systems must be adjusted.
When the distance between the two, right and left image sensing systems is short, the right and left images have no disparity with respect to a far object, and sufficient stereoscopic sense cannot be obtained. Hence, in such case, the distance between the two, right and left image sensing systems must be increased. In this manner, upon image sensing using the multi-eye image sensing apparatus, to adjust the base length and convergence angle in correspondence with each object is an important technical requirement.
The image sensing optical systems of the aforementioned multi-eye image sensing apparatus will be explained below with reference to FIG. 27. FIG. 27 depicts the layout of the image sensing optical systems in the conventional multi-eye image sensing apparatus.
In the conventional multi-eye image sensing apparatus, as shown in FIG. 27, the optical axis spacing (base length) and the angle the optical axes make with each other (convergence angle) are changed by mechanically moving the right and left image sensing optical systems. The conventional multi-eye image sensing apparatus is capable of sensing a so-called panoramic image, which has a broader angle in the horizontal direction, using two or more image sensing systems. Upon sensing the panoramic image, the plurality of image sensing optical systems are placed to be capable of sensing different fields of view by nearly matching their viewpoints each other, and minimizing the overlapping region between images required for joining the images sensed by the image sensing optical systems in an image process. In this case, the optical axis spacing and the angle the optical axes make with each other in the image sensing optical systems are mechanically adjusted.
On the other hand, recently, even in a non-coaxial optical system, an optical system in which aberrations can be satisfactorily corrected using an asymmetric aspherical surface as a constituent surface can be built by introducing the concept xe2x80x9creference axisxe2x80x9d, as disclosed in Japanese Patent Laid-Open Nos. 9-5650, 8-292371, and 8-292372. Japanese Patent Laid-Open No. 9-5650 discloses the design method of such optical system, and Japanese Patent Laid-Open Nos. 8-292371, and 8-292372 disclose its design examples.
Such non-coaxial optical system is called an offaxial optical system, which is defined as an optical system in which, assuming a reference axis along a light ray passing through the image center and pupil center, a normal to the surface at the intersection of a constituent surface with the reference axis contains a curved surface (offaxial surface) which is not present on the reference axis, and the reference axis at that time has a bent shape.
In this offaxial optical system, in general, since its constituent surfaces are offaxial and no eclipse is produced on a reflecting surface, an optical system using the reflecting surface can be easily build. Also, the optical path can be laid out relatively freely, and a one-piece optical system can be easily formed by forming constituent surfaces by one-piece molding.
However, in the above-mentioned conventional multi-eye image sensing apparatus, since the convergence angle and base length of its image sensing optical systems are changed by moving and rotating these optical systems, the entire apparatus becomes bulky if the image sensing optical systems are comprised of coaxial optical systems.
Especially, upon sensing a panoramic image, the right and left viewpoints must be nearly matched (i.e., the base length as the spacing between the centers of the entrance pupils of the respective image sensing optical systems must be set to be nearly zero). However, since the entrance pupil position cannot be largely moved toward the object side, when the convergence angle becomes equal to or larger than a predetermined angle, lenses in the respective image sensing optical systems may interfere with each other. As a consequence, the base length cannot become smaller than a predetermined length. Or if the base length is set at an appropriate length, a large convergence angle cannot be set.
In case of the multi-eye image sensing apparatus, the right and left image sensing systems must have uniform magnification and imaging performance. However, in the conventional apparatus, since a plurality of lenses are built in lens barrels in the right and left image sensing systems, the optical characteristics of the right and left image sensing systems suffer variations. Hence, the magnifications and the like in the right and left image sensing systems must be adjusted.
Furthermore, upon switching to the panoramic image sensing mode by increasing the convergence angle of the image sensing optical systems, since xe2x80x9ccentral viewpointsxe2x80x9d (xe2x80x9ccentral viewpointxe2x80x9d means a point on a line obtained by extending the reference axis of each image sensing optical system toward the object, and such point will be referred to as a xe2x80x9ccentral viewpointxe2x80x9d hereinafter) of the right and left image sensing optical systems are different from ideal ones of a synthesized image, an image process for removing apparent trapezoidal distortion arising from the xe2x80x9ccentral viewpointxe2x80x9d difference must be done upon joining the right and left images.
An example upon sensing a panoramic image will be described below with reference to FIGS. 28A to 28C. FIGS. 28A to 28C are views showing images sensed by panoramic image sensing of the conventional multi-eye image sensing apparatus, and an ideal synthesis result of those images.
Upon sensing a panoramic image using the two, right and left image sensing optical systems, since these systems have a convergence angle, as shown in FIG. 28A, they have different xe2x80x9ccentral viewpointsxe2x80x9d with respect to an object to be sensed, as shown in FIGS. 28B and 28C. More specifically, since the xe2x80x9ccentral viewpointsxe2x80x9d of the right and left image sensing optical systems are different from an ideal xe2x80x9ccentral viewpointxe2x80x9d of a synthesized image shown in FIG. 28C, an image process for removing apparent trapezoidal distortion arising from the xe2x80x9ccentral viewpointxe2x80x9d difference must be done upon joining the right and left images. However, when the trapezoidal distortion is removed by only the image process, the image quality deteriorates.
It is the first object of the present invention to provide a multi-eye image sensing apparatus, which can reduce the number of building components of image sensing optical systems, and can realize a compact arrangement.
It is the second object of the present invention to provide a multi-eye image sensing apparatus which can easily change the convergence angle without increasing the base length.
It is the third object of the present invention to provide a multi-eye image sensing apparatus which can easily change the base length.
It is the fourth object of the present invention to provide a multi-eye image sensing apparatus which can suppress variations of imaging performance.
It is the fifth object of the present invention to provide a multi-eye image sensing apparatus which can easily switch the image sensing mode between a three-dimensional image sensing mode and panoramic mode.
It is the sixth object of the present invention to provide a multi-eye image sensing apparatus which can obtain an image which suffers less apparent trapezoidal distortion arising from the difference between the right and left central viewpoints.
It is the seventh object of the present invention to provide a multi-eye image sensing apparatus which can selectively execute a three-dimensional image sensing mode and panoramic image sensing mode without making the apparatus bulky.
In order to solve the aforementioned problems and to achieve the above objects, according to the first invention, since at least one offaxial optical system block which includes an offaxial reflecting surface that is an asymmetric aspherical surface, and has a refractive power that can form a real image as a whole is provided to each of the image sensing systems, the number of building components of the respective image sensing systems can be reduced, and a compact arrangement can be realized.
Even when the image sensing systems are placed to have a small spacing between the image sensing elements, a large base length as the spacing between irises can be assured, and optical elements can be prevented from interfering with each other even upon setting a large convergence angle.
According to the second invention, since the offaxial optical system block includes an offaxial reflecting surface which is a vertically symmetric and horizontally asymmetric aspherical surface, and the offaxial optical system blocks are provided to the right and left image sensing systems upside down, the image sensing systems which have a smaller shape than the conventional image sensing systems in each of which lenses are built in a lens barrel, and have a small difference in optical characteristics such as imaging performance and the like between the right and left systems, can be realized.
According to the third invention, since the offaxial optical system block is prepared by molding, variations of imaging performance can be suppressed by setting constant forming conditions upon forming the blocks by one-piece molding of plastic, glass, or the like.
According to the fourth invention, since some or all components of the image sensing systems which include the offaxial optical system blocks are pivotal, and a three-dimensional image sensing mode in which the right and left image sensing systems have disparity, and a panoramic image sensing mode in which viewpoints of the right and left image sensing systems substantially match can be switched to one another by pivoting the some or all components, the three-dimensional image sensing mode and panoramic mode can be easily switched.
According to the fifth invention, since the right and left image sensing systems form images by producing trapezoidal distortions having horizontally reversed patterns, an image which suffers less apparent trapezoidal distortion due to the difference between the right and left central viewpoint can be obtained upon synthesizing a panoramic image. Hence, the image quality can be prevented from deteriorating upon removing that trapezoidal distortion by only the image process.
According to the sixth invention, since entrance and exit reference axes are located on different straight lines in the image sensing systems, the convergence angle and base length can be relatively freely set by exploiting high degree of freedom in layout of the entrance and exit reference axes.
According to the seventh invention, since the image sensing systems have an iris immediately before an object-side entrance surface, the base length as the spacing between irises can be shortened upon panoramic image sensing, and even in the layout of the image sensing systems with a large convergence angle, these image sensing systems including the iris can be prevented from interfering with each other.
According to the eighth invention, since the image sensing systems have an iris immediately before an object-side entrance surface of the offaxial optical system block, the offaxial optical system block and iris can be fixed by a single holding member, and a further size reduction of the apparatus can be attained.
According to the ninth embodiment, since each of the image sensing systems including the offaxial optical system blocks forms an image at least once in the middle of an optical path that extends to an imaging surface, the image sensing system can have a small shape.
According to the 10th invention, since some or all components of the image sensing systems which include the offaxial optical system blocks are pivotal, and a convergence angle the plurality of image sensing systems make is changed by pivoting the some or all components, the convergence angle can be easily changed without increasing the base length.
According to the 11th invention, since some or all components of the image sensing systems which include the offaxial optical system blocks are pivotal within a plane including exit reference axes of the offaxial optical system blocks, the convergence angle can be flexibly changed by adjusting the pivot amount in the plane including the exit reference axis.
According to the 12th invention, since some or all components of the image sensing systems which include the offaxial optical system blocks are pivotal, and a base length of the plurality of image sensing systems make is changed by pivoting the some or all components, the base length can be easily changed.
According to the 13th invention, since some or all components of the image sensing systems which include the offaxial optical system blocks are pivotal about exit reference axes of the offaxial optical system blocks, the base length can be flexibly changed by adjusting the pivot amount about the exit reference axis.
According to the 14th invention, since the plurality of image sensing systems are constructed to be able to switch between a three-dimensional image sensing mode for producing disparity between the right and left image sensing systems, and a panoramic image sensing mode for substantially matching viewpoints of the right and left image sensing systems with each other, by exchanging the offaxial optical system blocks, the three-dimensional image sensing mode and panoramic image sensing mode can be selectively executed without making the apparatus bulky.
According to the 15th invention, a plurality of reflecting surfaces that make surface reflection are formed on the offaxial optical system block, and an incoming light beam exits the offaxial optical system block after the light beam repeats reflection on the reflecting surfaces.
According to the 16th invention, since the plurality of image sensing systems have a three-dimensional image sensing optical block for producing disparity between the right and left image sensing systems, and a panoramic image sensing optical block for substantially matching viewpoints of the right and left image sensing systems with each other, the three-dimensional and panoramic image sensing optical blocks comprise offaxial optical system blocks each of which includes an offaxial reflecting surface that is an asymmetric aspherical surface as a building component, and has a refractive power that can form a real image, and the three-dimensional and panoramic image sensing modes can be switched to one another by switching between the three-dimensional and panoramic image sensing optical blocks, the three-dimensional image sensing mode and panoramic image sensing mode can be selectively executed without making the apparatus bulky.
According to the 17th invention, the three-dimensional and panoramic image sensing optical system blocks are placed in an identical plane.
According to the 18th invention, the three-dimensional and panoramic image sensing optical system blocks are stacked parallel to a plane including a reference axis.
According to the 19th invention, the offaxial reflecting surface of each of the offaxial optical system blocks is an aspherical surface which is vertically symmetric and horizontally asymmetric, and the offaxial optical system blocks are built in the right and left image sensing systems upside down.
According to the 20th invention, each of the offaxial optical system blocks is prepared by molding.
According to the 21st invention, a plurality of reflecting surfaces that make surface reflection are formed on the offaxial optical system block, and an incoming light beam exits the offaxial optical system block after the light beam repeats reflection on the reflecting surfaces.
According to the 22nd invention, since the plurality of image sensing systems form images by producing trapezoidal distortions having horizontally reversed patterns upon sensing an image in the panoramic image sensing mode, a further size reduction of the apparatus can be attained.
According to the 23rd invention, the plurality of image sensing systems are constructed to have entrance and exit reference axes located on different straight lines.
According to the 24th invention, since the plurality of the image sensing systems perform intermediate imaging at least once in the middle of an optical path that extends to an imaging surface, a further size reduction of the apparatus can be attained.
According to the 25th invention, since the plurality of image sensing systems perform intermediate imaging at least once in the middle of an optical path that extends to a final exit surface, a further size reduction of the apparatus can be attained.
According to the 26th invention, in a multi-eye image sensing apparatus having a plurality of image sensing systems, since each of the plurality of image sensing systems has at least one offaxial optical system block which includes an offaxial reflecting surface that is an asymmetric aspherical surface as a building component, and has a refractive power that can form a real image, each offaxial optical system block includes a three-dimensional image sensing optical path for producing disparity between the right and left image sensing systems, and a panoramic image sensing optical path for substantially matching viewpoints of the right and left image sensing systems with each other, and three-dimensional and panoramic image sensing modes can be switched to one another by switching between the three-dimensional and panoramic image sensing optical paths by rotating the offaxial reflecting surface in the offaxial optical system block, the three-dimensional image sensing mode and panoramic image sensing mode can be selectively executed without making the apparatus bulky.
According to the 27th invention, the offaxial reflecting surface of each of the offaxial optical system blocks is an aspherical surface which is vertically symmetric and horizontally asymmetric, and the offaxial optical system blocks are built in the right and left image sensing systems upside down.
According to the 28th invention, each of the offaxial optical system blocks is prepared by molding.
According to the 29th invention, a plurality of reflecting surfaces that make surface reflection are formed on the offaxial optical system block, and an incoming light beam exits the offaxial optical system block after the light beam repeats reflection on the reflecting surfaces.
According to the 30th invention, since the plurality of image sensing systems form images by producing trapezoidal distortions having horizontally reversed patterns upon sensing an image in the panoramic image sensing mode, a further size reduction of the apparatus can be attained.
According to the 31st invention, the plurality of image sensing systems are constructed to have entrance and exit reference axes located on different straight lines.
According to the 32nd invention, since the plurality of image sensing systems have an iris immediately before an object entrance surface, a further size reduction of the apparatus can be attained.
According to the 33rd invention, since the plurality of the image sensing systems perform intermediate imaging at least once in the middle of an optical path that extends to a final exit surface, a further size reduction of the apparatus can be attained.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.